Prjetummry This Revision extends the goals of EY16187 towards defining causal relationships between the timing and category of intensive early experience and the modular organization of the temporal lobe. The goals of EY16187 are to use functional MRI (fMRI) and single-unit recording to explore the mechanisms underlying the formation of category selective modules in inferotemporal cortex. Early results in this project have produced an animal model in which juveniles with extensive early experience in recognizing symbols develop regions in their temporal lobes that are selectively responsive to the learned symbols, with concomitant behavioral expertise. Adult learners show less behavioral expertise and no novel module formation. This result suggests the hypothesis that the modular organization of the temporal lobe is not entirely innate, but is determined, or modified, by neuronal activity. To test this hypothesis this Revision will extend the project to look at functional re-organization in two additional sets of animals: (1) animals trained to recognize two different symbol sets at different stages of development and (2) animals trained to recognize face-like images as inanimate representations of value. The first experiment will use a double cross over training design to ask how the timing of category specific experience affects the localization of novel modules. The second experiment will ask whether intensive early exposure to abnormal face-like stimuli can disrupt the normal organization of face modules. These studies will expand the goal of understanding of how neuronal activity can affect the organization of high-level perceptual mechanisms by specifically looking for causal relationships between experience and modular organization. The implications for education policy and for mental health are significant. For understanding autism spectrum disorders and for understanding consequences of early deprivation and abnormal early experience it is important to know how malleable brain organization is, and whether something as basic as face-processing domains is innate, or if such domains are molded by social experience and can be modified by abnormal experience.